<template>
 <div class="todo-footer">
        <label>
          <input type="checkbox" v-model="isCheckAll"/>
        </label>
        <span>
          <span>已完成{{count}}</span> / 全部{{todos.length}}
        </span>
        <button class="btn btn-danger" @click="clearAllCompletedTodos" >清除已完成任务</button>
      </div>

  </template>

<script lang="ts">
  import {computed, defineComponent} from 'vue'
  import {Todo} from '../types/todo'
  export default defineComponent({
    name:'Footer',
    props:{
      todos:{
        type:Array as ()=>Todo[],
        required:true
      },
      checkAll:{
        type:Function,
        required:true
      },
      clearAllCompletedTodos:{
        type:Function,
        required:true
      },
    },
    setup(props){
const count=computed(()=>{
  return props.todos.reduce((pre,todo,index)=>pre+(todo.isCompleted?1 : 0),0),0
})
//全选或者全不选的计算属性操作
const isCheckAll = computed({
      get() {
        return count.value > 0 && props.todos.length === count.value
      },
      set(val) {
        props.checkAll(val)
      },
    })
  

      return{
        count,
        isCheckAll,
   
      }
    }
  })
</script> 

<style scoped>
.todo-footer {
  height: 40px;
  line-height: 40px;
  padding-left: 6px;
  margin-top: 5px;
}

.todo-footer label {
  display: inline-block;
  margin-right: 20px;
  cursor: pointer;
}

.todo-footer label input {
  position: relative;
  top: -1px;
  vertical-align: middle;
  margin-right: 5px;
}

.todo-footer button {
  float: right;
  margin-top: 5px;
}
</style>

